1. Field of the Invention
The present invention relates to an optical interconnection technique and, in particular, to the structure of an optical wiring circuit.
2. Description of the Related Art
To connect together a plurality of microprocessors and memories there has been generally used an electric bus circuit. However, in the case of the electric bus circuit, a signal delay caused by inter-connection-wiring capacity and connection wiring resistance limits the processing speed of a system using the electric bus circuit. When trying to make more dense a parallel-bus connection wiring, there arises a problem that an electromagnetic noise occurs; that is, it has been more and more difficult for the electric bus circuit to cope with the high-speed bus processing. In view of this, there has been proposed an optical interconnection technique in which the electric wiring is replaced with an optical wiring to enhance the speed of the bus.
For example, in JP-B-Hei. 6-22351, there is disclosed a technique in which two sets of light-emitting/light-receiving devices are disposed in both surfaces of each of circuit boards and the light-emitting/light-receiving devices on the mutually adjoining circuit boards incorporated into a system frame are connected together in terms of space by light. However, in the disclosed technique, since light/electricity conversion is necessary for every communication between the mutually adjoining circuit boards, the cost is expensive and the delay amount is large. Also, because the light is transmitted through a free space, the optical/electric element is difficult to position and is also weak against crosstalk and dust.
In JP-B-Hei. 6-93051, there is disclosed a technique in which there is provided a plate having two parallel surfaces and disposed opposed to a light source, a diffraction grating and a reflecting element are respectively disposed on the two surfaces of the plate, a free space defined by the diffraction grating and reflecting element is used to form an optical path, and circuits are optically connected together through the optical path. However, in this disclosed technique, because it aims at realizing one-to-one communication, the light emitted from one point is connected to the other only one fixed point; and thus, communication is possible neither between one point and other multiple points nor between multiple points and multiple points.
In JP-A-2000-329962, which was previously filed by the present applicants, there is disclosed a structure in which a planer optical waveguide is disposed on an optical circuit board and optical wave guides each formed of optical fibers are connected to both sides of the planer optical waveguide. However, in the disclosed structure, no attention is paid to arrangement and structure of the other end of the optical wave guide; that is, the other end of the optical wave guide is extended from the side surface of the optical circuit board and thus, to connect the optical circuit board with another optical circuit board or an electric wiring circuit, the optical wave guide must be bent in a complicated manner, which makes it difficult to position the other end of the optical wave guide.
In view of the related art circumstances, it is an object of the invention to provide a structure of an optical wiring circuit which not only is simple in structure but also is capable of facilitating the connection of the optical wiring circuit with another optical wiring circuit or an electric wiring circuit. Also, it is a second object of the invention to provide an optical wiring circuits layered body which is capable of light communication between multiple points and multiple points. Further, it is a third object of the invention to provide an optical/electric wiring apparatus which is reduced in the delay amount and is strong in coping with crosstalk and dust.